Urinary system Flashcards
urinary system function:
- eliminate waste products through formation of urine
- activate vit D
- produce erythropoietin
contribute to regulation of:
- arterial blood pressure
- pH of body fluids
- vol and comp of blood
- blood glucose levels
kidney: features
- post to peritoneum
- within abdominal cavity
- R kidney lower than L
- T12-L3 level
kidney: surrounded by main layers
- renal capsule
- perinephric fat
- renal fascia
- paranephric fat
kidney function: renal capsule
- dense ct
- barrier to fat
kidney function: perinephric fat
- protects kidney
- holds in place
kidney function: renal fascia
- fibrous tissue
- anchors kidney to surrounding structures
kidney function: paranephric fat
- protection
kidney: main internal parts
- renal cortex
- renal medulla
kidney: renal cortex
superficial layer of kidney + renal columns
kidney: renal medulla
renal pyramids - papillary ducts - minor calyces (via renal papilla) - major calyces - renal pelvis - ureter
drainage system fills renal sinus cavity
nephron: comprised of
- renal corpuscle
- proximal convoluted tubule
- loop of Henle
- distal convoluted tubule
nephron: renal corpuscle =
glomerular capillaries + bowman’s capsule
several nephrons drain into:
collecting duct
many collecting ducts drain into:
papillary duct
nephron: classified as
- cortical (80-85%)
- juxtamedullary
nephron: cortical
- renal corpuscles in outer part of cortex
- short loop of Henle, mainly in cortex
nephron: juxtamedullary
- renal corpuscles in inner part of cortex
- long loop of Henle, mainly in medulla
- very important for concentrating/ diluting urine
nephron: renal corpuscle - glomerulus
- capillaries which contain blood from body to be filtered
nephron: renal corpuscle - bowman’s capsule
- double walled surrounding glomerulus
- receives filtrate from glomerulus (water, solutes)
nephron: tubules - proximal convoluted tubules
- receives filtrate from bowman’s cap
- microvilli maximise reabsorption/ secretion
- 65% filtered H2O, nearly 100% solutes reabsorbed
- H+, ammonium, urea, creatinine secreted
nephron: tubules - loop of Henle
- descending/ ascending limb
- receives filtrate from PCT
- reabsorb water, sodium, potassium, chloride, secrete urea
- urine conc
- macula densa (cell at distal cell) help monitor conc of sodium, chloride in filtrate
nephron: tubules - distal convoluted tubules
- receives filtrate from loop of Henle
- most of tubule is involved in reabsorption of water, sodium, chloride
- more distal part of tubule: principle cells and intercalated cells
nephron: tubules - DCT principle cells
- reabsorb water, sodium, urea and secrete potassium
- respond to ADH and aldosterone
nephron: tubules - DCT intercalated cells
- reabsorb bicarbonate and urea and secrete hydrogen
nephron: drainage - collecting ducts
- receive filtrate from 1+ nephron
- contain principle and intercalated cells
- drain into papillary duct
nephron: no. of nephrons
- remains constant from birth
- no replacement
- dysfunction occurs when function declines by 25%
- removal of 1 kidney causes enlargement of remaining until it can filter at 80% of normal rate of 2 kidneys
blood supply to kidney:
- R and L renal aa
- R and L renal v
blood supply pathway in kidney:
abdominal aorta - renal aa - segmental aa - interlobar aa (btw pyramids) - arcuate aaa- interlobular aa (renal columns) - afferent arterioles - glomerular capillaries - efferent arterioles - peritubular capillaries/ and or vasa recta
kidney: 3 major activities
- glomerular filtration
- tubular reabsorption
- tubular secretion
kidney: glomerular filtration
- movement of plasma into bowman’s capsule
- filtrate comprises of all blood except cells, platelets, most proteins
regulated by:
- arterial blood pressure
- nervous system
- endocrine system
kidney: tubular reabsorption
- movement of water and solutes from filtrate within nephron and back into blood vessels
- osmosis
- simple diffusion
- facilitated absorption
- active transport
generally:
- 99% water
- 99.5% sodium
- 100% glucose
- 44% urea
kidney: tubular secretion
- movement of substances from blood into filtrate
important substances secreted:
- potassium
- hydrogen and ammonium (help control pH of body fluids)
- creatinine
- some drugs
kidney: where does tubular reabsorption occur
- tubules
- loop of Henle
- collecting ducts
kidney: where does tubular secretion occur
- tubules
- loop of Henle
- collecting ducts
arterial blood pressure: determined by
- cardiac output
- peripheral resistance
- blood vol
kidney principally influences:
- blood vol
- also peripheral resistance
- juxtaglomerular apparatus vital
juxtaglomerular apparatus: parts
- macula densa
- juxtaglomerular cells in wall of afferent arteriole
- extraglomerular mesangial cells btw afferent and efferent arterioles
lowered arterial BP or blood vol =
- lower blood in renal vessels - lower stretch of afferent arterioles - juxtaglomerular cells secrete renin
angiotensin II does:
- constricts efferent arterioles
- releases aldosterone
- release ADH
- stimulate thirst
result: constrict efferent arterioles
increase in glomerular filtration pressure
result: release aldosterone/ ADH
reabsorption of more water, increase blood vol
result: stimulate thirst
increase blood vol
ureters: features
- retroperitoneal
- enters post wall of bladder
- physiological valve (bladder wall compresses ureteral opening as it expands during filling)
- flow results from peristalsis, gravity and hydrostatic pressure
urinary bladder: apex
- points to upper part of pubic symphysis
- connected to ant ab wall near umbilicus by median umbilical lig
urinary bladder: base
- shaped like inverted triangle
- face postero-inf
- ureters enter at upper corners
- urethra exits from lower corner
- muscosa smooth (trigone)
urinary bladder: superior surface
slightly domed when empty, more so when full
urinary bladder: 2 inferolateral surfaces
btw levator ani and obturator internus
urinary bladder: neck
- most inf
- surrounds urethral opening
- anchored by pair of fibromuscular bands -> posteroinferior parts of pubic bones
urinary bladder: females- anterior
pubis
urinary bladder: females- posterior
- uterus
- vagina
urinary bladder: females- superior
- uterus
- small intestine
urinary bladder: females- inferior
N/A
urinary bladder: females- inferolateral
pelvic diaphragm
urinary bladder: males- anterior
pubis
urinary bladder: males- posterior
- rectum
- seminal vesicles
- ampulla of ductus deferens
urinary bladder: males- superior
small intestine
urinary bladder: males- inferior
prostate
urinary bladder: males- inferolateral
pelvic diaphragm
urinary bladder: layers in wall
- mucosa
- muscularis (aka detrusor)
- adventitia
urinary bladder: mucosa
- transitional epithelium and lamina propria
- mucus protect cells from urine
- in rugae not trigone
urinary bladder: muscularis
- 3 layers of smooth muscle
- circular smooth mm -> internal urethral sphincter
- circular skeletal mm -> external urethral sphincter
urinary bladder: adventitia
- loose ct anchors it in place
- superior surface has serosal layer
micturition reflex: step 1
- bladder holds 700-800ml urine
- vol > 200-400 stretch receptors stimulated
- impulses sent to sacral spinal cord -> sensation of fullness/ desire to urinate
micturition reflex: step 2
- micturition reflex centre in sacral spinal cord
- without this, reflex motor response cause bladder to contract
- everything healthy will send inhibitory/ facilitatory signals to reflex centre
micturition reflex: step 3
- if appropriate time to urinate, facilitatory impulses descend from brain - sacral spinal cord = reflex triggered
- efferent pathway involves parasympathetic fibres -> detrusor mm contract, int sphincter mm relax
micturition reflex: step 4
- urine enters urethra sends impulses to S2-4
- decrease activity of pudendal n -> allow ext urethral sphincter relax
- conscious control of ext sphincter
micturition reflex: step 5
urination occurs
urethra: female
- directed anteroinferior
- opens into vestibule
- inf part bound to ant wall of vagina
urethra: male
- tube passes through prostate, urogenital diaphragm and penis
- prostatic, membranous, spongy urethra (sometimes preprostatic part)
- opens at tip of glans penis (ext urethral orifice)
- circular smooth mm forms int urethral sphincter
- urogential diaphragm forms ext urethral sphincter
